Calibration of acoustic emission sensors
Kolář, Petr; Petružálek, Matěj
2017 - English
Measurement of acoustic emission (AE) during laboratory experiments – rock sample loading - is an important tool for study of material mechanical properties as well as understanding of modes of its failure. For correct data processing it is necessary to calibrate used AE sensors. The calibration constants can depend on property of individual sensors, on their contact conditions, etc. As there can be a deformation induced charge in sensor contact condition, the calibration constants may vary with time. AE sources can be modeled (in the same way as natural earthquakes) as double couple sources with use of moment tensor (MT) formalism (3x3 symmetric tensor, i.e. 6 independent values, the problem is linear). We adopted method, which enable calibration of an individual station of a seismic network. The method is based on simultaneous determination of MTs and calibration constant(s). During the experiment there were repeatedly measured velocities of elastic waves by ultrasonic sounding, when AE sensors cyclically acted as sources. We processed this data and for each cycle determined calibration constant for all the sensors but one, which is supposed to be 1. The source is supposed to be of single force type, which further reduces number of determined parameters. The evaluation was performed cyclically for all the sensors, the final calibration constants are then the mean values.
Keywords:
acoustic emission; sensors calibration; ultrasonic soundingAvailable at various institutes of the ASCRCalibration of acoustic emission sensors

Measurement of acoustic emission (AE) during laboratory experiments – rock sample loading - is an important tool for study of material mechanical properties as well as understanding of modes of its ...

Increase of annual and seasonal air temperatures in the Czech Republic during 1961-2010
Střeštík, Jaroslav; Rožnovský, J.; Štěpánek, P.; Zahradníček, P.
2016 - English
Using the monthly means of air temperatures at 267 stations in the Czech Republic, the long-term change has been estimated at each station for the last 50 years. Annual mean temperatures for the whole country show a considerable increase, more pronounced than that for global temperature, however, supplemented by strong fluctuations from year to year. Long-term changes in air temperatures at different stations and in different regions vary. Stronger increase in air temperatures can be seen in Bohemia, whereas in Moravia temperature increase is not so significant. This difference is more pronounced in the winter, whereas in the summer, the differences are smaller and perhaps of opposite nature. This means that the continentality of the climate in Moravia increases, while in Bohemia it very slightly decreases. Long-term changes depend only marginally on the absolute values of annual mean temperatures at the respective station. The increase of autumn temperatures is considerably lower than that of other seasons.
Keywords:
air temperatures; long-term change; regions; seasonsAvailable at various institutes of the ASCRIncrease of annual and seasonal air temperatures in the Czech Republic during 1961-2010

Using the monthly means of air temperatures at 267 stations in the Czech Republic, the long-term change has been estimated at each station for the last 50 years. Annual mean temperatures for the whole ...

Verification of model calculations for the Kaplan turbine design
Polák, M.; Polák, Václav; Hudousková, M.
2016 - English
In order to design a water turbine, the Theory of the Physical Similarity of Hydraulic Machines is used in technical practice. This principle has been known and used by manufacturers of turbines and pumps, but is not available to general public. This paper describes author's calculation program for turbine design that is well accessible to the widest possible range of users of mainly small hydropower sources. Based on the given hydraulic potential (water head and flowrate), the program determines the most suitable turbine type and calculates its main geometric parameters. In addition to numerical results, the program is also endowed with graphic output which renders in true scale hydraulic profiles of rotor blades and guide blades as well as the hydraulic profile of a spiral casing. The process of the Kaplan turbine design is used as an example in this paper. The comparisons of the calculated results with the verified standard 4-K-69 Kaplan turbine confirm the compliance of numerical results with reality.
Keywords:
blade geometry; calculation program; theory of physical similarityAvailable at various institutes of the ASCRVerification of model calculations for the Kaplan turbine design

In order to design a water turbine, the Theory of the Physical Similarity of Hydraulic Machines is used in technical practice. This principle has been known and used by manufacturers of turbines and ...

Detailed analysis of (selected) West Bohemian earthquakes - results and possible geological consequences
Kolář, Petr
2015 - English
At TCP 2011 and 2013 we informed about Interactive tool for determination of parameters of finite seismic source model using Stopping Phases method. Now the crucial part of software is developed and the Tool is in routine operation: events are analysed, values of investigated parameters are obtained and in addition the harvested results seem to yield also information about detailed geological structure in the foci area - such knowledge cannot be obtained by another way unless the exhaustive and expensive prospecting geophysical methods are applied. Namely we processed sets of events from pronounced seismic swarms which occurred in West Bohemia in yrs. 2000, 2008 and under the investigation are 2011 data (2014 data are the challenge for the future).
Keywords:
West Bohemia seismic swarms; finite seismic source; data processingAvailable at various institutes of the ASCRDetailed analysis of (selected) West Bohemian earthquakes - results and possible geological consequences

At TCP 2011 and 2013 we informed about Interactive tool for determination of parameters of finite seismic source model using Stopping Phases method. Now the crucial part of software is developed and ...

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